1. Technical Field
The invention relates generally to air springs and, in particular, to air springs having an internal bumper which acts as a back-up in case of air spring failure or to absorb sudden large deflections or shocks imparted on the air springs. Specifically, the invention relates to a block of an elastomeric material, such as a thermoplastic, that can be installed into the compartments of a bumper in various numbers and configurations to control the compressive elastic characteristics of the bumper.
2. Background Information
Pneumatic springs, commonly referred to as air springs, have been used for motor vehicles and various machines and other equipment for a number of years to provide cushioning between movable parts, primarily, to absorb shock loads and vibration damping imparted thereon. The air spring usually consists of a flexible rubber sleeve which extends between a pair of end members and which contains a supply of compressed air and may have one or more pistons located at ends of the flexible sleeve. The end members mount the air spring on spaced components or parts of the vehicle or equipment on which the air spring is mounted.
The internal pressurized fluid, which is generally air, absorbs most of the shock impressed upon or experienced by one of the spaced end members on which the air spring is mounted, with the ends members moving axially toward and away from each other upon absorbing the imparted shock. Examples of such air springs are shown in U.S. Pat. Nos. 4,787,606, 4,852,861, 4,946,144 and 5,201,500.
Certain of these prior art air springs have internal bumpers mounted on one of the end members which extends into the interior of the pressurized chamber. The bumper prevents total collapse or deflection of the air spring member in the event of air spring failure. The bumper also absorbs shock whenever the spring experiences severe shocks and deflections which result in actual or near "bottoming out " of the air spring member.
While these prior art bumpers are satisfactory for most applications, such bumpers still have a number of shortcomings related to their use. Particularly, the use of such bumpers has not been well suited to applications wherein the bumper is expected to experience a high number at a fast rate of extreme shocks inasmuch as such extreme shocks have resulted in complete deflection of the bumper without sufficient isolation of the extreme shocks from the structures mounted on the air spring.
Another problem that occurs in the use of air springs is that when a vehicle such as a truck is at rest, the air is released from within the air spring and the internal bumper supports the weight without any fluid pressure assistance. Occasionally, the driver will then start and drive the vehicle before the air spring is fully inflated and severe shock can be impressed upon the partially inflated bumper causing severe damage thereto.
Most prior art air springs are formed of a single elastomeric material which provides a compromise in order to absorb most of the shocks which are exerted thereon yet which is sufficiently pliable to prevent permanent damage or breaking of the bumper should a severe shock be applied thereto.
A need thus exists for an improved air spring bumper that can withstand the extreme shocks that are experienced in certain applications and which can have multiple configurations suited to different loading applications.
Examples of other devices including shock-absorbing components are set forth in the following patents.
U.S. Pat. No. 3,658,314 discloses a fluid shock absorber having an elastomeric member mounted between two concentrically movable tubes with an elastomeric bumper mounted beneath the inner tube to absorb impact from the tube.
U.S. Pat. No. 4,218,599 discloses a polymer spring for use in a drawer of a cabinet to ensure that when the drawer is closed, it does not rebound to a partially open position.
U.S. Pat. No. 4,342,264 shows another type of air spring using an elastomeric bumper mounted on one of the end members.
U.S. Pat. No. 4,478,396 discloses an elastomeric bumper which is mounted on the top of a vehicle strut.
U.S. Pat. No. 4,506,910 discloses a bumper mounted on the inner surface of a mounting plate of the air spring, whereby the bumper provides a limit to any extreme swinging of the beam attached to the piston opposed to the mounting plate.
U.S. Pat. No. 4,787,606 shows a rubber bumper attached to the inner surface of one of the end plates by a pin where the rubber bumper serves to prevent total collapse or deflection of the spring assembly.
U.S. Pat. No. 4,925,224 discloses an energy-absorbing bumper with an elastomeric bumper module. The energy-absorbing bumper is attachable to a vehicle where it serves to absorb the energy of an impact of that vehicle with another object.
U.S. Pat. No. 5,201,500 shows an air spring in which a post is mounted on one of the end members and extends into the fluid chamber where a shock-absorbing bumper is formed and snap-fitted on the enlarged top of the post.
However, no known device, including those discussed above, disclose an air spring having an internal bumper that receives one or more elastomeric blocks of material into cavities formed in the bumper to allow the bumper to withstand extreme shock loading, the bumper having a number of different configurations suited to different loading applications.